A rail bogie, which is also known as a railroad truck, wheel truck, or truck, is a rolling support structure that is pivotally connected at one end of a rail vehicle. The bogie includes suspension systems and axles having wheels that allow the rail carriage or locomotive to travel over a railway. In a typical configuration, a rail carriage includes two, pivotally connected bogies on its underside. Bogies are typically placed close to the ends of the carriages and include structures for releasably being connected to bogies of adjacent carriages or locomotives.
A typical bogie functions to support of the rail vehicle body, provide ride stability to the rail vehicle during travel on straight or curved railway sections, and improve ride quality for cargo and passengers by absorbing vibration and managing the effects of centrifugal forces, especially when the rail vehicle travels over curves at high speeds.
Most bogies have two axles, and each axle has two wheels. Other configurations, e.g. bogies providing traction to locomotives or bogies used for particularly high load applications, may include more than two axles. Usually, the floor of the rail vehicle is situated at a level generally above the bogie, at the top of a frame or platform. The frame may include an enclosure for cargo or passengers, and may be specially tailored to suit the particular application for the rail vehicle. The main structures of a bogie are the frame, suspension, one or more wheelsets, each wheelset including an axle with bearings and a wheel at each end, and an axle box, which absorbs shocks between the axle bearings and the bogie frame. Typical bogie applications may further include brake equipment such as shoes that are pressed against the tread of the wheel, or disc brakes that are pressed against pads attached to the axles. In powered applications, the bogies may further include motive equipment such as a transmission, electrically powered traction motors, torque converters, and the like.
A typical connection between the bogie and the rail vehicle is arranged to allow for rotational movement around a vertical axis pivot, which is also known as a bolster, with side bearers preventing excessive movement. In certain more modern applications, bolsters can be omitted. The relative rotation between the bogie and the frame of the rail vehicle allows the rail and you the vehicle to traverse curves in the tracks.
While bogies have been used for decades in rail travel, the pivotal connection at the bolster, or its modern variations, may not be best suited for the most efficient train operation possible. For example, uneven rail vehicle loading may cause increased rolling resistance, decreased traction and increased wear between the bogie and the tracks.